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Abstract:
The efficiency of vibration-based energy harvesters is often constrained by low vibration amplitudes and limited responsiveness beyond the resonant frequency. To overcome these limitations, mechanical amplifiers and spring bumpers can be employed to enhance excitation amplitude and magnet velocity within a compact device. This study presents a nonlinear oscillator supported on pre-compressed coil springs with high-stiffness bumpers acting as motion limiters. The resulting collision effects and friction introduce hysteresis, significantly influencing the system’s dynamic response. An electromagnetic model with position-dependent inductance is developed, and the identified system parameters enable numerical analysis of energy recovery and dynamic behaviour. Selected numerical predictions are compared with experimental observations, demonstrating the model’s effectiveness.

Keywords:
energy harvesting, nonlinear electromagnetic circuit, electromechanical systems, electromagnetic transduction, hysteresis phenomena, broadband response

Abstract:
The main drawback of vibration-based energy harvesting is its poor efficiency due to small amplitudes of vibration and low sensitivity at frequencies far from resonant frequency. The performance of electromagnetic energy harvester can be improved by using mechanical enhancements such as mechanical amplifiers or spring bumpers. The mechanical amplifiers increase range of movement and velocity, improving also significantly harvester efficiency for the same level of excitation. As a result of this amplitude of motion is much larger comparing to the size of the electromagnetic coil. This in turn imposes the need for modelling of electromagnetic circuit parameters as the function of the moving magnet displacement. Moreover, high velocities achieved by the moving magnet reveal nonlinear dynamics in the electromagnetic circuit of the energy harvester. Another source of nonlinearity is the collision effect between magnet and spring bumpers. It has been shown that this effect should be carefully considered during design process of the energy harvesting device. The present paper investigates the influence of the above-mentioned nonlinearities on power level generated by the energy harvester. A rigorous model of the electromagnetic circuit, derived with aid of the Hamilton's principle of the least action, has been proposed. It includes inductance of the electromagnetic coil as the function of the moving magnet position. Additionally, nonlinear behaviour of the overall electromagnetic device has been tested numerically for the case of energy harvester attached to the quarter car model moving on random road profiles. Such a source of excitation provides wide band of excitation frequencies, which occur in variety of real-life applications.

Keywords:
energy harvesting, velocity amplification, nonlinear electromagnetic circuit, spring bumper, quarter car model

Abstract:
The paper presents application of the MFC actuator and selected control algorithms to the suppression of the composite cantilever beam vibrations. The first part concentrates on the identification of the real structure’s parameters. The numerical model is based on the Euler-Bernoulli beam theory with a nonlinear curvature component. The second part draws on numerical simulations and leads to the identification of optimal control parameters. Finally, the determined parameters are examined in an experimental laboratory system equipped with a DSP controller.

Keywords:
MFC actuator, control algorithm, active beam, DSP controller